The glycosyltransferase UGT76E1 significantly contributes to 12-O-glucopyranosyl-jasmonic acid formation in wounded Arabidopsis thaliana leaves

Abstract

Jasmonoyl-isoleucine (JA-Ile) is a phytohormone that orchestrates plant defenses in response to wounding, feeding insects, or necrotrophic pathogens. JA-Ile metabolism has been studied intensively, but its catabolism as a potentially important mechanism for the regulation of JA-Ile–mediated signaling is not well-understood. Especially the enzyme(s) responsible for specifically glycosylating 12-hydroxy-jasmonic acid (12-OH-JA) and thereby producing 12-O-glucopyranosyl-jasmonic acid (12-O-Glc-JA) is still elusive. Here, we used co-expression analyses of available Arabidopsis thaliana transcriptomic data, identifying four UDP-dependent glycosyltransferase (UGT) genes as wound-induced and 12-OH-JA–related, namely, UGT76E1, UGT76E2, UGT76E11, and UGT76E12. We heterologously expressed and purified the corresponding proteins to determine their individual substrate specificities and kinetic parameters. We then used an ex vivo metabolite-fingerprinting approach to investigate these proteins in conditions as close as possible to their natural environment, with an emphasis on greatly extending the range of potential substrates. As expected, we found that UGT76E1 and UGT76E2 are 12-OH-JA-UGTs, with UGT76E1 contributing a major in vivo UGT activity, as deduced from Arabidopsis mutants with abolished or increased UGT gene expression. In contrast, recombinant UGT76E11 acted on an unidentified compound and also glycosylated two other oxylipins, 11-hydroxy-7,9,13-hexadecatrienoic acid (11-HHT) and 13-hydroxy-9,11,15-octadecatrienoic acid (13-HOT), which were also accepted by recombinant UGT76E1, UGT76E2, and UGT76E12 enzymes. UGT76E12 glycosylated 12-OH-JA only to a low extent, but also accepted an artificial hydroxylated fatty acid and low amounts of kaempferol. In conclusion, our findings have elucidated the missing step in the wound-induced synthesis of 12-O-glucopyranosyl-jasmonic acid in A. thaliana.

The Effect of Recombinant Tags on Citrus paradisi Flavonol-Specific 3-O Glucosyltransferase Activity

“…Initial characterizations of pH optima for Cp3GT, obtained through expression in E. coli, indicated an optimal pH of 7-7.5, which is indicative of a normal physiological pH. This agrees with other flavonoid glucosyltransferase (GT) pH optima of 6.5-8 [25][26][27]. More recent characterizations of Cp3GT expressed using P. pastoris, however, showed a higher optimal pH of 8.5-9.…”

Recent Advances in Plant Chemical Biology of Jasmonates

“…Considering that 12-OH-JA-Ile accumulates 10-fold higher levels than JA-Ile at a later stage and the high concentration level continues more than 8 h, the moderate and biased JAZ degradation by 12-OH-JA-Ile may fine-tune late jasmonate responses. 12-OH-JA-Ile can be further converted to 12-COOH-JA-Ile by CYP94C1 [67], 12-OH-JA by IAR3&ILL6 [70], 12-O-Glc-JA by UGT76E1 [71], and 12-HSO 4 -JA by ST2a ( Figure 5C) [72]. Among them, only 12-O-Glc-JA is biologically active in a plant, causing leaf-folding movement of Samanea saman in COI1-independent manner [73].…”

Integrated proteomic and metabolomic analyses reveal the importance of aroma precursor accumulation and storage in methyl jasmonate-primed tea leaves

“…In addition, the accumulation of hydroxylated JA glycosides appears to be another strategy; however, to date, the mechanism has not been determined. Glycosylation conjugates secondary metabolites in plants, which facilitates the storage and transport of hydrophobic substances and reduces their activity by blocking reactive hydroxyl groups 34 , 35 . UGTs are key for the conversion of secondary metabolites to various glycosides.…”

“…The different activities of these glycosyltransferases toward different aroma substrates could be a major reason for the accumulation of various glycosides in MeJA-primed tea leaves, which was also confirmed by another study 35 . In addition, various families of UGTs, which play key roles in the glycosylation of phenolic compounds, were identified 43 – 45 . Further characterization of UGTs will shed more light on the mechanisms triggering the release of volatiles and the accumulation of glycosidically bound precursors.…”